Chromis viridis: All About the Blue Green Chromis

Some fish just have it all. Colorful, easy to keep, reef safe, suitable for smaller tanks… can it get any more perfect? The blue green chromis is one of these species. If you’re a beginner looking for fish to stock your first marine aquarium with, this one makes an excellent choice.

Below, find everything you need to know to make sure your chromis thrive!

Blue green chromis description & natural habitat

Description

The blue green chromis is a species of damselfish. Belonging to the family Pomacentridae along with their ultra-popular clownfish cousins, the damsels are aquarium classics appreciated for their small size, lovely colors, and easy care. In fact, the blue green chromis has been the most commonly traded aquarium fish of all for years!

It’s not difficult to see where the blue green chromis got its common name. Its shimmery, almost iridescent coloration does indeed fall somewhere between blue and green depending on the light. They reach a maximum length of around 4″, although most don’t make it past 3″.

Did you know? The blue green chromis is not always blue and green. Males, during the mating season, completely change color! They turn more of a yellow green with some black coloration. If you see the males turning this color in the aquarium, that’s a good indication your chromis are getting frisky.

Natural habitat

The blue green chromis is a typical reef fish. It has a wide Indo-Pacific distribution and can be found all the way from the African coast (including the Red Sea) to as far east as the Pitcairn Islands.

In their natural range, these damsels prefer the shallows. They inhabit reef flats and lagoons of a depth up to around 65ft and particularly appreciate the safety afforded by “forests” of branching Acropora corals, which is where they’re most commonly spotted.

The species can form large, loosely aggregated groups known as shoals, which helps confuse predators and allows them to hunt their tiny prey (mostly plankton) more efficiently.

Blue green chromis aquarium

Although they’re quite small, blue green chromis are very active fish. This should be reflected in the size of the aquarium you keep yours in. A group of 6-8 fish needs at least around 75 gallons to thrive (more about why we consider this the minimum group size below in the section on compatibility).

Keep in mind that these little damselfish depend on the shelter provided by Acropora and other corals in the wild. An open environment makes them feel unsafe, so it’s a good idea to fill the tank with plenty of coral and live rock formations for them to dart around. Knowing they have a safe place to retreat to in case of danger will actually make them more bold and active!

Although they’re mainly considered inhabitants of the middle water layer, you’ll find your blue green chromis actively exploring all corners of the aquarium.

Tip: Although blue green chromis are hardy and forgiving as far as reef fish go, they will still suffer if you let the water quality drop. Ensure the tank is fully cycled before introducing any livestock and perform regular water changes to keep your chromis happy and healthy.

Blue green chromis compatibility

Damselfish are generally not exactly known for their ability to play nice with their neighbors. Many species are notoriously territorial and can bully tankmates, including those much larger than them, relentlessly. The blue green chromis is a nice exception to this rule!

When it comes to their neighbors, these damselfish know how to play nice. They’re peaceful and unlikely to bother their tankmates, meaning you can combine them with a wide variety of other calm reef species. If you’re a beginner, may we suggest our favorite easy saltwater aquarium fish?

As for reef safety, you’re in luck here too. This reef dweller is not known for bothering corals or invertebrates. The only tankmates you should actively avoid are larger or overly aggressive ones that might bully the small blue green chromis.

Chromis-on-chromis violence

One thing you do need to keep in mind about this fish is that while interspecies aggression is very rare with blue green chromis, in-group behavior is more unpredictable. Aquarists commonly report cases of “missing fish syndrome”, where the victim is likely to be deceased but has already been eaten by its (invertebrate) tankmates.

The problem is that most folks either don’t provide enough space, or keep their blue green chromis in small groups. The former means territorial fights are more likely to break out, while the latter can result in fish that are lower on the social ladder being bullied so relentlessly they eventually give up the ghost.

You can opt to keep only a single chromis to prevent all this, but that seems a little sad for such a social species. Plus, you’d miss out on all those interesting social interactions! By giving these fish plenty of space and keeping a group of at least 6-8 individuals, you should be able to prevent most (territorial) squabbles.

Tip: Even if you provide plenty of space and keep a sizable group of blue green chromis, mysterious disappearances can still occur in the first few weeks after acquiring yours. This is usually because they don’t travel that well, with the trips to the aquarium store and then to your house sometimes proving fatal. We recommend buying chromis that have been at the store for at least a week or so, plus a long quarantine period to catch common infections that tend to affect damselfish (such as uronema).

Blue green chromis diet

The blue green chromis is an omnivorous species. It mostly feeds on small critters like plankton, copepods and amphipods, but has also been found to consume algae.

In the aquarium this is not a difficult feeder at all. It should accept pretty much anything you offer it, including commercial flake and pellet foods for marine fish. A far cry from some of the ultra-picky reef species in the hobby!

As variety is the spice of life, you can also opt to include (thawed) frozen foods like artemia, krill and mysis. Algae tabs or blanched veggies may also be appreciated.

Tip: Don’t over-clean the aquarium walls and rocks. Your blue green chromis will appreciate it if you leave a patch of algae for them to graze on.

Breeding blue green chromis

Sorry, not much luck here! Fat and healthy blue green chromis will sometimes spawn without any interference on your end. The males take on their breeding colors—yellowish with a black dorsal fin—and begin trying to woo the females, who sometimes progress to laying eggs.

That’s unfortunately where things end in the aquarium. Raising the teeny tiny larvae has proven to be incredibly hard due to their fragility and free-swimming nature, which is why commercial hatcheries usually don’t bother. After all, it’s incredibly easy and cheap to catch blue green chromis in the wild!

Wild blue green chromis, like many other fish, are synchronized lunar spawners. This means they come together in large groups to reproduce, in this case around both the full and new moon marks. Males begin to establish small breeding sites, which are then visited by females looking for a suitable partner and location.

Once a male chromis and his nesting site have been approved, the female will deposit her eggs. Mom doesn’t stick around, but dad does, at least for a while. Once the eggs hatch, parents and larvae go their own way.

Basically: yes, Chromis viridis reproduction has been cracked. Indian researchers managed it in 2009, as did the Tropical Aquaculture Laboratory in 2013. But if you want to breed saltwater fish at home, may we recommend something easier like clownfish instead?

Conclusion

A bustling reef tank with a group of shimmering blue green chromis really is quite a sight to see. We think Chromis viridis is one of the best aquarium fish for beginners, and they also make a great choice for more experienced aquarists who just want something simple.

Are you dreaming of an aquarium for your home or office? FantaSEA can help. Contact us with your ideas and let’s make it happen!